It is well established that the transition from the current linear economy model to a circular one requires a novel approach for waste management. In other words, residues must be seen as feedstock for other processes instead of valueless materials. Within the domain of biofuels, for example, waste conversion into energetic molecules (e.g., ethanol, biodiesel, and biogas) is a suitable alternative to fossil fuels, and it has been developed successfully. Similarly, other value-added molecules can also be obtained from residues and avoid producing such molecules from nonrenewable feedstocks. Accordingly, if an industrial facility produces energetic and other marketable molecules from waste materials, i.e., a spectrum of bio-based products, it can be called a “biorefinery.” Considering this context, bio-oil production emerges as a promising technology, capable of providing biofuels and high-value-added molecules while contributing to waste management. In that regard, this chapter, through an introductory approach, addresses bio-oil production processes, possible bio-oil applications, the potential of this waste valorization process in a biorefinery context, and the advances in bio-oil research.